To the left is a chart of conservative, moderate and liberal voters as a percent of the total vote in 2004, 2008 and 2012 presidential elections.
The only category in which 2012 out performed the previous two elections is in the liberal vote for the Democratic candidate.
The Obama campaign beat the drum that this was a liberal vs. conservative election. Did the electorate want to go back to the failed policies of the past and let the rich off from paying "their fair share"? The Democrats also added the "social" issue of abortion and forcing all employers to provide free contraceptives. In other words, the Obama campaign used the dog whistles that political pundits for years have been saying would lose a presidential campaign. The key, experts assured us, is appealing to moderates and independents. Not this election.
The Romney campaign followed "expert" advice and did not emphasize the conservative/liberal divide. They emphasized managerial competence. Romney could create more jobs. They stayed away from social issues and even constitutional 1st and 2nd amendment rights issues. They banked on the "It's the economy, stupid" theme of 1992.
But, for the electorate, the economy did not trump ideology and social issues. Romney actually lost in moderate vote percentage compared with George W. Bush in 2004 (16.8% vs. Bush's 20.3%) and McCain in 2008 (16.8% vs. McCain's 17.2%). And Obama did too (22.96% vs. his 2008 26.4% and Kerry's 2004 24.3%). But, it didn't sink Obama's campaign because he made up for the loss of moderates with increased liberal support.
Romney lost this election because he did not excite his conservative base by pounding conservative issues as Obama pounded liberal issues.
Had Romney been able to equal the Gallup poll percentage with conservative voters (let alone over-perform as Obama did with liberal voters), he would have won the election with an additional 5 million votes.
The big vote addition is due to the fact that even though enthusiastic liberals were 25% of this election's voters, conservatives still made up 35% of voters--a 10% difference.
It turns out running on ideology and principle really can win elections. Ronald Reagan proved that in 1980. And, this election proved it again.